High-speed rotation drum for use with a centrifugal separator for gaseous mixture

ABSTRACT

A drum structure adapted to be rotated at a high-speed for the centrifugal separation of gaseous mixture. The drum is of a composite structure comprising a first drum part and a second drum part disposed on the outer periphery of the first drum part. The latter is made of a metal which is resistant to the corrosion by the gaseous mixture while the second drum part is made of a plastic material reinforced with a large number of fibers wound and extending circumferentially. The second drum part is composed of a plurality of ring-like members each of which is shorter than the first drum part whereby the manufacture of the drum is simplified.

United States Patent 1191 Kadotani et al.

[ Mar. 19, 1974 HIGH-SPEED ROTATION DRUM FOR USE WITH A CENTRIFUGAL SEPARATOR FOR GASEOUS MIXTURE [75] Inventors: Kenzo Kadotani; Tokio Isogai;

' Yasushi Miyano, all of Hitachi;

Katsuhito Suzuki, Mito, all of Japan [30] Foreign Application Priority Data 2.008.037 7/1935 Quantin 233/1 R P IIIAIIII IIIYI/l 3,145,174 8/1964 Ambler 233/46 X 2,879,282 3/1959 Afzelius 233/46 X FOREIGN PATENTS OR APPLICATIONS 18,793 8/1965 Japan 233/27 593,432 2/1934 Germany 233/27 473,870 5/1951 Canada 233/27 Primary Examiner-George H. Krizmanich Attorney, Agent, or Firm-Craig and Antonelli [5 7] ABSTRACT A drum structure adapted to be rotated at a highspeed for the centrifugal separation of gaseous mixture. The drum is of a composite structure comprising a first drum part and a second drum part disposed on the outer periphery of the first drum part. The latter is made of a metal which is resistant to the corrosion by the gaseous mixture while the second drum part is made of a plastic material reinforced with a large number of fibers wound and extending circumferentially. The second drum part is composed of a plurality of ring-like members each of which is shorter than the first drum part whereby the manufacture of the drum is simplified.

11 Claims, 9 Drawing Figures Pmmmmw 1914 3.797.737

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INVENTORS KENZO KAnoTAm romo 150 M,

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ATTORNEYS e ral speed which exceeds 400 m/sec. The ability of the 11 HIGH-SPEED ROTATION DRUM FOR USE WITH A CENTRIFUGAL SEPARATOR FOR GASEOUS MIXTURE BACKGROUND OF THE INVENTION Gaseous materials such as UF are separated either by a gas-dispersion diaphragm process or by centrifural separation process. The present invention is concerned with the centrifugal separation process. The centrifugal separation and concentration of UF is carried out in such a manner that a quantity of UP is introduced into a drum rotating at a high speed to place the quantity in a centrifugal field so that UP is urged by the centrifugal force against the inner peripheral surface of the drum. At this time, large pressure gradient is generated in UF so that the latter is separated by the pressure dispersion into a required gas and unnecessary ones. The required gas thus obtained will be further subjected to a similar process which is repeated to ultimatelyproduce a concentrated quantity of gas.

It has been found that the concentration of UF by means of the centrifugal separation process is more economical than by the gas-dispersion diaphragm process if the high-speed rotation drum attains its periphcentrifugal separation bf UP varies in proportion to the peripheral speed of the high-speed rotation drum to the fourth, so that a little increase or decrease in the peripheral speed greatly influences the ability of the separation. In the certrifugal separation process, therefore, efforts have been made to increase the peripheral speed of the high-speed rotation drum of the centrifugal separator. m For this purpose, it is required that the high-speed rotary drum be made of a material having a large tensile strength in circumferential direction and a small density, i.e., a material of a large specific tenacity. Among metallic materials, extra super duralmin is considered to be most suited for the high-speed rotation drum of a gaseous material centrifugal separator while a plastic material reinforced with circumferentially wound fibers is believed to beappropriate for the purpose among non-metallic materials. Researches and tests are being made on these materials in the art.

Extra super duralmin provides insufficient specific tenacity for the high-speed rotary drum while a fiberreinforced plastic material has its specific tenacity sufficient to enable the drum to withstand a peripheral speed higher than 400 m/sec. However, in the case where a plastic material concerned is reinforced with glass fibers, the reinforced plastic material is not practicable because glass fibers are weakened by corrosive gas, HF, produced by UF under the presence of water. A fiber other than glass fibers, such as carbon fibers, is

resistant to the corrosion by HF. However, the mechan- 5 ical strength of carbon fiber is reduced by a radiation material such as uranium contained in UP In order to solve the problems above discussed, the inner peripheral surface of the high-speed rotation drum of a fiber-reinforced plastic may be coated with a layer of a HF-resistant and radiation-resistant material as by vaporizing a HF-resistant and radiation resistant metal onto the inner surface of the drum. Such a layer would be quite advantageous if the coated drum could be used in stationary condition. However. the

drum is intended to be rotated at a high speed. During rotation, the drum will be subjected to various kinds of forces which tend to cause the drum to be so deformed that the vaporized metal layer is peeled off the drum. Thus, the operation of a drum with a vaporized metal layer thereon will be quite dangerous.

The use of a high-speed rotation drum which is simply made of a fiber-reinforced plastic material only will be quite dangerous. Specifically, the high-speed rotation drum of a fiber-reinforced plastic is reinforced with fibers which are wound and extend in circumferential direction of the drum so as to increase the circumferential tensile strength thereof while the drum provides lesser axial tensile strength. This tends to allow the drum to be easily damaged if the drum is subjected to axial tensile stress during high-speed rotation.

In order that the axial tensile strength of the fiberreinforced plastic drum may be improved, an attempt has been made to wind the fibers to extend in a direction at an angle with respect to the circumferential direction of the drum. This attempt somewhat increases the axial tensile strength of the drum but greatly decreases the strength and modulus of elasticity in the circumferential direction of the drum with a disadvantageous result that the allowable limit of the speed of the There has been developed a composite high -speed rotation drum composed of metallic and non-metallic materials. More specifically, the drum includes a first drum part of a metal such as extra super duralmin which is resistant to the corrosive action of UP The metal provides insufficient specific tenacity for the drum part to withstand the rotation at a required highspeed and, thus, is reinforced with a second drum part provided on the outer peripheral surface of the first drum part. The second drum part is made of a fiberreinforced plastic material having a large specific tenacity. This arrangement provides a drum which will withstand high-speed rotation in that the first drum part deals with thecorrosion and the axial tensile stress while the second drum part bears the circumferential tensile stress.

The composite drum is manufactured by the following method: First of all, the first drum part is accurately worked. Then, fibers are wound on the outer peripheral surface of the worked first drum part as by filamentwinding process. A plastic material is then cured on the fibers to form a second drum part which is then worked to finish the outer peripheral surface thereof. However, the first drum part is apt to be damaged during the formation of the second drum part, i.e., when the fibers are wound and the plastic is cured by heat. Moreover, if a crack is formed in the second drum part during the surface finishing thereof, the second drum part becomes useless in its entirety. For this reason, particular attention, a great amount of labour and time are required for the formation of the second drum part. In addition, filaments have to be wound over the entire length of the first drum part. This not only requires substantial amount of time but also need skilled and experienced technique to provide the second drum part with a uniform quality. Furthermore, since the first and second drum parts are united or secured together at an earlier stage of manufacture, the adjustment for balanced rotation of the drum involves very difficult work.

There is an alternative method of making a drum of this kind. This method includes the steps of preparing the first and second drum parts separately and securing the parts together either by shrinkage fit or by providing the parts with tapered mating surfaces. In any way,

since the drum parts may be respectively adjusted for balanced rotation before they are secured together, a resultant composite drum may be balanced for rotation with the first drum part not deformed.

Since the first drum part is made of a metal and thus is of a uniform density throughout, the drum part may be easily adjusted for balanced rotation by precisely working the part. However, since the second drum part is made of a fiber-reinforced plastic material, it is inevitable for the second drum part to have areas in which the ratio of fiber content with respect to a unit of mass of the material of the second drum part is different from a similar ratio in other areas. This causes uneven density of the second drum part and. thus, makes it difficult to adjust the part for balanced rotation. It will be appreciated that, since a drum of this kind is elongated, i.e., cm in diameter and 200 cm in length as an example, it is in fact difficult to adjust such an elongated body for balanced rotation.

Normally, the opposite ends of a high-speed rotation drum are supported and closed by end plates. During high-speed rotation, the axially central portion of the drum is expanded to an increased diameter by the centrifugal force while the opposite ends of the drum are subjected to lesser expansion as compared with the central portion. The difference in the expansion does not cause much problem on the first drum part which is made of a metal while the difference will cause cracks to be produced in the second drum part of a fiber-reinforced plastic material. More specifically, since the second drum part is reinforced with circumferentially extending fibers, the drum part exhibits a large tensile strength in the circumferential direction as discussed in the above. The drum part, however, provides a lesser tensile strength in the axial direction. For this reason, when the drum is subjected to bending stress along the length thereof, the second drum part is subjected to compression on the inner side thereof while the outer side is subjected to tensile stress which causes cracks to be produced in the second drum part.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a composite high-speed rotation drum for use with a centrifugal separator for gaseous materials which drum can be easily manufactured. It is another object of the present invention to provide a composite high-speed rotation drum of the class specified in the preceding paragraph and which can easily be adjusted for balanced rotation.

It is a further object of the present invention to provide a composite high-speed rotation drum of the class specified and which can withstand the bending stress produced along the length of the drum during operation thereof.

It is a still further object of the present invention to provide a composite high-speed rotation drum of the class specified and which sustains minimized damage during the manufacture and operation of the drum.

According to the present invention. there is provided a composite high-speed rotation drum for use with a centrifugal separator for gaseous materials, said drum comprising a first drum part of a metal and a second drum part of a fiber-reinforced plastic material fitted onto the outer peripheral surface of said first drum part, wherein said second drum part comprises a plurality of annular members each of which is shorter than said first drum part.

Other objects and features of the present invention will be made apparent by the following description with reference to the accompanying drawings.

DESCRIPTION OF DRAWINGS FIG. 1 is a longitudinal partial sectional view of a centrifugal separator equipped with a high-speed rotation drum according to the present invention;

FIG. 2 is an enlarged partial longitudinal sectional view illustrating the details of the drum according to an embodiment of the invention;

FIG. 3 is a similar view but illustrating another embodiment of the invention;

FIG. 4 is a fragmentary longitudinal sectional view of a drum according to a further embodiment of the invention;

FIG. 5 is a view similar to FIG. 4 but illustrating a drum according to a still further embodiment of the invention;

FIG. 6 is a fragmentary side elevation of a drum according to a still further embodiment of the invention;

FIG. 7 is a diagrammatic fragmentary longitudinal sectional view illustrating the drum shown in FIG. 6 in its operation; and

FIGS. 8 and 9 are fragmentary longitudinal sectional views of still further embodiments of the invention illustrating modified connections between drums of the invention and end plates, respectively.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring first to FIG. 1, there is shown a centrifugal separator for separating gaseous materials such as UF Generally, the separator comprises a high-speed rotation drum 1, bearing means rotatably supporting the drum 1 and a drive means 13 for rotating the drum 1 at a high-speed.

The high-speed rotation drum 1 is vertically positioned and has its opposite ends secured to end plates 4A and 4B which hermetically close the drum 1. Hollow shafts 5A and 58 extend outwardly from the central portions of the end plates 4A and 48, respectively. The shafts 5A and 5B are coaxial with drum 1 and communicate the interior of the drum with the exterior thereof. The shafts 5A and 5B are rotatably supported at the ends by bearings 10B and 10C mounted on frmae members 7, 8 and 14 surrounding the drum 1.

A thinner tube 6 is disposed within the hollow shaft 5A with spacers positioned therebetween and extends coaxially with the shaft 5A. The tube 6 has its upper end portion extending upwardly beyond the upper end of the hollow shaft 5A while the lower end portion of the tube 6 extends into the high-speed rotation drum 1. The tube 6 has mounted thereon a disc 6A disposed within the drum 1 adjacent the end plate 4A. The upper end of the tube 6 is rotatably supported by a bearing 10A which in turn is secured to frame members 9A and 9B. Adjacent the ends of the hollow shafts 5A and 5B and the tube 6, gas chambers 11A, 11B and 11C separated one from another are defined by the bearings 10A, 10B and 10C and the frame members 9A, 9B and 9C, respectively. A gas supply conduit 12A is connected to the gas chamber 11A while gas discharge conduits 12B and 11C are connected to the gas chambers 11B and 12C. respectively. Within the frame member 8 is provided a drive means such as an electric motor 13 for rotating the drum 1 at a high-speed. A heater is mounted on the inner surface of the frame member 7 at a level corresponding to the upper portion of the drum l.

The separator of the above-described arrangement is operative to separate gaseous materials such as UF Specifically, the drive means 13 is energized to rotate the drum at a high speed and the heater 15 is also energized to heat the outer peripheral surface of the upper portion of the drum 1. A quantity of UF is introduced into the gas chamber 11A through the supply conduit 12A. The gaseous material is then passed through the tube 6 into the drum 1 in which the materialis subjected to strong centrifugal force until the material is separated into gases. Under the influence of the temperature gradient within the drum 1, one of the separated gases flows through the gap between the end plate 4A and the disc 6A into the hollow shaft 5A from which the gas flows through the gas chamber 1 18 at the end of the shaft 5A and through the discharge conduit 128 into a container (not shown). The other gas flows through the hollow shaft 58 at the bottom of the drum 1 into the gas chamber 11C from which the gas is passed through the discharge conduit 12C into another container (not shown).

Referring now to FIG. 2, the high-speed rotation drum 1 includes a first or inner drum part 2 made of a metal such as, for example, extra super duralmin, which has a large specific tenacity and is resistant to the corrosive and deteriorating action of the gaseous material. On the outer periphery of the first drum part 2, are provided a plurality of axially arranged shorter sleeve or annular members 3A, 3B, 3C and 3D formed from a fiber-reinforced plastic material such as, for example,

epoxy resin reinforced with glass or carbon fibers extending circumferentially of the annular members. The inner'drum part 2 and the annular members 3A, 3B, 3C and 3D are respectively adjusted for balanced rotation before they are assembled and secured together into a completed drum by any conventional fitting process such as shrinkage fit or providing the members with tapered mating surfaces.

The arrangement shown in FIG. 2 provides an advantage that the annular members 3A, 3B, 3C and 3D which form the second part of the drum 1 deal with the circumferential tensile stress produced by a high-speed rotation of the drum while the first or inner drum part 2 deals with the axial tensile stress and the corrosive and deteriorating action of the gaseous materials to be separated.

In addition. each of the shorter annular members 3A, 3B. 3C and 3D can be made precisely within a shortened time and. moreover, can be relatively easily adjusted for balanced rotation. It will be appreciated that, if the second or outer drum part is of a unitary structure which consists of an elongated tubular member as in the case of the prior art, it is extremely difficult and requires a great amount of time to make the quality of the second drum part uniform. Moreover, the annular membes 3A, 3B, 3C and 3D are each shorter than the first drum part 2, the work on the members, such as winding of filamentous fibers, can be completed in a shortened time. Also,each of the annular members can be formed to have uniform quality. Furthermore, the variation in the ratio of fiber content per unit of length of each annular member is minimized to enable the adjustment for balanced rotation to be minimized and simplified.

The present invention provides an additional advantage that, if one of the annular members of the second drum part is damaged during the manufacture or operation of the drum 1, the damaged annular member alone may be replaced with another one rather than the second drum part being placed in its entirety. Thus, the high-speed rotation drum according to the present invention is quite economical.

The invention provides a further advantage that, even if one of the annular members 3A, for example, should be damaged, the damage does not befall to the other annular members because the second drum part is composed of a plurality of separate annular members. To the contrary, with a second drum part which is of a unitary structure as in the prior art drum structure, if a crack is produced in an area of the second drum part during rotation thereof, the crack will rapidly grow and will be extended to other areas to break the drum part.

A description will then be made with respect to another embodiment shown in FIG. 3. The high-speed rotation drum of this embodiment comprises a first drum part 2 of a metal covered with a second drum part which consists of a plurality of axially arranged annular members 3A, 31A, 31B, 31C and 3D of plastic materials reinforced with circumferentially extending fibers. The embodiment shown is substantially identical with the preceding embodiment except that the annular members 3A and 3D are made of a carbon fiberreinforced plastic material while the other annular members 31A, 31B and 31C are made of a glass fiberreinforced plastic material. It will be remembered that the drum 1 of the embodiment shown in FIG. 2 has its annular members 3A to 3D all made of a plastic material reinforced with glass fibers or carbon fibers.

It is to be noted that a carbon fiber-reinforced plastic material has a greater mechanical strength and, more particularly, the tensile strength in the direction of the fibers than those of a glass fiber-reinforced plastic material. Thus, the annular members of a second drum part all made of a carbon fiber-reinforced plastic material will satisfy the requirement. However, a carbon fiber-reinforced plastic material is very expensive as compared with a glass fiber-reinforced plastic material. It will, therefore, be economical to employ annular members 31A to 31C of a glass fiber-reinforced plastic material at the portions or sections of the second drum part where the glass fiber-reinforced plastic material meet with the mechanical strength requirement. This concept of the invention is employed in the embodiment shown in FIG. 3. Namely, since the opposite ends of the drum I are secured to the end plates E A and 48, respectively, the annular members 3A and 3D of a carbon fiber-reinforced plastic material are positioned at the ends of the second drum part so as to largely reinforce the portions of the drum adjacent the connections to the end plates while the annular members 31A to 31C of a glass fiber-reinforced plastic material are positioned in the axial center sections of the second drum part where a lesser mechanical strength is required than at the ends of the second drum part.

A certain type of centrifugal separator for gaseous materials is designed such that the outer periphery of the upper portion of the high-speed rotation drum 1 is heated to produce a temperature gradient within the drum so as to facilitate the separation of the gaseous materials. The drum 1 is deformed to have an increased larger diameter at the heated portion than at the other portions along the length of the drum. This deformation subjects the connections between the drum 1 and the end plate 4A to undue stress and results in damage of the drum.

A high-speed rotation drum 1 shown in FIG. 4 is designed to withstand the undue stress caused by the deformation due to the heating of the drum. More specifically, the drum of the embodiment shown in FIG. 4 comprises a first drum part 2 of a metal such as extra super duralmin and a second drum part fitted on the outer periphery of the drum part 2. The second drum part is composed of a plurality of axially arranged annular members 32A to 32E of a plastic material reinforced with fibers such as, for example, carbon fibers. The thickness of the second drum part is largest at the section of the drum where the same is heated. The thickness is reduced step by step toward the end of the drum remote from the heated portion of the drum. In other words, the annular member 32A positioned at the upper end ofthe drum 1 is of the largest thickness while the annular member 325 positioned at the lower end of the drum 1 is of the smallest thickness. With this arrangement. since the portion of the drum 1 at which the greatest deformation takes place due to the heat and rotation is strongly reinforced with the annular member 32A of a less-deformable carbon fiber-reinforced plastic material and having the largest thickness, the deformation of the drum is minimized.

The annular members 32A to 32E according to the instant embodiment have substantially the same axial dimension and gradually reduced thickness because the temperature gradient in the drum 1 of the instant embodiment due to the heating is substantially linear, highest at the top of the drum and lowest at the bottom thereof.

In the case where the temperature gradient is curvilinear as is in a case where the heat is applied solely to the upper portion of the drum and substantially no heat is applied to the other portions of the drum along the length thereof. the drum 1 preferably has the arrangement illustrated in FIG. 5. The second drum part according to the instant embodiment comprises a plurality of axially arranged annular members 33A to 33F of a fiber-reinforced plastic material fitted over the first drum part 2 which is similar to that of preceding embodiments. The annular members 33A to 33F are of gradually reducing thickness; the upper-most annular member 33A is of the largest thickness while the lowermost annular member 33F is of the smallest thickness. In addition. the annular members are of gradually increasing length (L L the two upper-most annular members 33A and 33B are each of the smallest length (L) while the two lower-most annular members 33E and 33F are each of the largest length (L Various kinds of combination of the annular members 33A to 33F of different length and thickness can be employed to comply with various kinds of temperature gradients in order that the deformation of high-speed rotation drums may be minimized.

In general, the high-speed rotation drum is secured at the opposite ends to end plates. If the amount of distortion of the end plates due to the centrifugal force during operation of the separator is different from that of the high-speed rotation drum, these members are caused to have different radii which bend the portions of the drum adjacent the ends thereof with a result that the second drum part of a fiber-reinforced plastic material is subjected to bending stress. It will, therefore, be appreciated that the second drum part is operated in such a condition as to be liable to be damaged in that the drum and, particularly, the second drum part is reinforced in circumferential direction only and thus does not provide a sufficient mechanical strength to deal with the forces exerted to the drum part in the other directions. The embodiment shown in FIGS. 6 and 7 is designed to overcome this problem. Namely, the drum of this embodiment has a first drum part 2 secured at the end to an end plate 4A. Annular members 34A, 34B, 34C are fitted over the first drum part 2. Those of the annular members which are positioned adjacent the end plate 4A, i.e., adjacent the portion of the drum which receives the bending stress, are designed to have smaller axial dimension than those of the other annular members so as to be able to follow the bend of the first drum part 2 of the drum. Thus, even if the portion of the drum adjacent the end plate 4A is caused to have an amount of distortion differentiated from that of the central part of drum during rotation thereof to cause the first drun part to be bent, the portion of the second drum part adjacent the end plate 4A can follow and accommodate the bend of the first drum part 2 in that the portion of the second drum part is composed of shorter annular members 34A, 34B, 34C and 34D. In addition, the bending stress does not act on these shortened annular members 34A, 34B, 34C and 34D. Thus, the second drum part is not subjected to the damage or risk of damage which would otherwise take place as in the case of a unitary or single structure second drum part.

FIGS. 8 and 9 each illustrate an example of the connection between the high-speed rotation drum and end plate. In the example shown in FIG. 8, the end plate 4A is formed with an annular groove 48 opened in both of the peripheral surface and bottom or inner surface of the plate. The second drum part 2 of the drum 1 is engaged at one end with the annular groove 48. In the example shown in FIG. 9, formed in one of the side faces of the end plate 4A is an annular groove 4G into which the first drum part 2 of the drum 1 is fitted at one end thereof. Annular members 3B forming the second drum parts of the embodiments shown in FIGS. 8 and 9 may be employed in common with both embodiments except that the embodiments need different uppermost annular members 35 and 36 to be disposed adjacent the end plates 4A, respectively, because the embodiments are differentiated in the design of the connection between the end plate 4A and the first drum part 2. In addition, the annular members 38 which are intended to be located at the portions of the drum remote from the end plate 4A cannot be mounted adjacent the same. Thus. with the type of a high-speed rotation drum that has second drum part of a single or unitary structure, a different design of second drum part must be prepared for a different type of connection between the first drum part and an associated end plate. However, with the type of a high-speed rotation drum that has a second drum part consisting of a plurality of annular members, mass-produced annular members may be commonly utilized on high-speed rotation drums of different types of connection between the first drum part and the end plate except that a different type of annular member must be mounted on the drum of a different type of drum-end plate connection at the portion of the drum adjacent the end plate. Thus, a highspeed rotation drum can be manufactured in a shortened time.

As described in the above, the present invention provides a composite high-speed rotation drum comprising a first and second drum parts, said second drum part being fitted over said first drum part and consisting of a plurality of axially arranged annular members each shorter than the first drum part. This structure not only eases the manufacture of a high-speed rotation drum but also makes it simplified to adjust the drum for balanced rotation. The sectionalized or separated structure of the second drum part is very economical in that, if a part of the second drum part is damaged during the manufacture and operation of the drum, the damage can be minimized and that the damaged annular member alone may be replaced with another one.

In addition, the annular members forming the second drum part may have varied or different thicknesses and lengths so that the members may form a second drum part which can withstand the forces exerted thereto by the deformation of the first drum part and which can prevent the first drum part from being unduely deformed by the temperature differential along the length thereof in the case where the drum is of a design that is subjected to temperature gradient. Thus, the invention provides a reliable high-speed rotation drum.

Moreover. the annular members of the second drum part may be formed from different materials which can be appropriately combined for the most economical manufacture of the second drum part.

What we claim is:

1. A composite high-speed rotation drum for use with a centrifugal separator for gaseous materials, said drum comprising a first drum part of a metal and a second drum part including a plurality of axially arranged annular sleeve members, each member having an axial dimension shorter than said first drum part and each member being formed of fiber-reinforced plastic material fitted onto the outer peripheral surface of said first drum part, wherein said plurality of annular members being axially adjacent to one another.

2. A drum as claimed in claim 1, in which said annular members are made of a carbon fiber-reinforced plastic material.

3. A drum as claimed in claim 1, in which said annular members are made of a glass fiber-reinforced plastic material 4. A drum as claimed in claim 1, in which said first drum part is made of extra super duralmin and said annular members are made of a carbon fiber-reinforced plastic material.

5. A drum as claimed in claim 1, in which some of said annular members are made of a carbon fiberreinforced plastic material and the remaining annular members are made of a glass fiber-reinforced plastic material.

6. A drum as claimed in claim 1, in which said annular members have different thicknesses.

7. A drum as claimed in claim 1, in which said annular members have different lengths.

8. A drum as claimed in claim I, in which said annular members have different thicknesses and different lengths.

' 9. A drum as claimed in claim 1, in which said fiberreinforced plastic material of the annular members includes fibers extending circumferentially 10. A drum as claimed in claim 1, in which said first and second drum parts are cylindrically-shaped.

11. A drum as claimed in claim 1, in which said annular members are securely fitted to the outer peripheral surface of said first part. 

1. A composite high-speed rotation drum for use with a centrifugal separator for gaseous materials, said drum comprising a first drum part of a metal and a second drum part including a plurality of axially arranged annular sleeve members, each member having an axial dimension shorter than said first drum part and each member being formed of fiber-reinforced plastic material fitted onto the outer peripheral surface of said first drum part, wherein said plurality of annular members being axially adjacent to one another.
 2. A drum as claimed in claim 1, in which said annular members are made of a carbon fiber-reinforced plastic material.
 3. A drum as claimed in claim 1, in which said annular members are made of a glass fiber-reinforced plastic material
 4. A drum as claimed in claim 1, in which said first drum part is made of extra super duralmin and said annular members are made of a carbon fiber-reinforced plastic material.
 5. A drum as claimed in claim 1, in which some of said annular members are made of a carBon fiber-reinforced plastic material and the remaining annular members are made of a glass fiber-reinforced plastic material.
 6. A drum as claimed in claim 1, in which said annular members have different thicknesses.
 7. A drum as claimed in claim 1, in which said annular members have different lengths.
 8. A drum as claimed in claim 1, in which said annular members have different thicknesses and different lengths.
 9. A drum as claimed in claim 1, in which said fiber-reinforced plastic material of the annular members includes fibers extending circumferentially
 10. A drum as claimed in claim 1, in which said first and second drum parts are cylindrically-shaped.
 11. A drum as claimed in claim 1, in which said annular members are securely fitted to the outer peripheral surface of said first part. 